Method for ultrasonic welding a coaxial cable to a coaxial connector

ABSTRACT

A coaxial connector for interconnection with a coaxial cable with a solid outer conductor by ultrasonic welding is provided with a monolithic connector body with a bore. An annular flare seat is angled radially outward from the bore toward a connector end of the connector, the annular flare seat open to the connector end of the connector. An inner conductor cap is provided for interconnection with an inner conductor of the coaxial cable by ultrasonic welding. The ultrasonic welding of each of the inner and outer conductor interconnections may be performed via inner conductor and outer conductor sonotrodes which are coaxial with one another, without requiring the cable and or connector to be removed from their fixture.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of commonly owned co-pending U.S. Utility patent application Ser. No. 12/980,013, titled “Ultrasonic Weld Coaxial Connector and Interconnection Method” filed Dec. 28, 2010 by Kendrick Van Swearingen, hereby incorporated by reference in its entirety. This application is also a continuation-in-part of commonly owned co-pending U.S. Utility patent application Ser. No. 12/974,765, titled “Friction Weld Inner Conductor Cap and Interconnection Method” filed Dec. 21, 2010 by Kendrick Van Swearingen, hereby incorporated by reference in its entirety. U.S. Utility patent application Ser. Nos. 12/980,013 and 12/974,765 are each a continuation-in-part of commonly owned co-pending U.S. Utility patent application Ser. No. 12/951,558, titled “Laser Weld Coaxial Connector and Interconnection Method”, filed Nov. 22, 2010 by Ronald A. Vaccaro, Kendrick Van Swearingen, James P. Fleming, James J. Wlos and Nahid Islam, hereby incorporated by reference in its entirety.

BACKGROUND

1. Field of the Invention

This invention relates to electrical cable connectors. More particularly, the invention relates to a coaxial connector and method and apparatus for interconnection of such coaxial cable connector with a coaxial cable via ultrasonic welding wherein the interconnection may be performed with a single fixture mounting operation.

2. Description of Related Art

Coaxial cable connectors are used, for example, in communication systems requiring a high level of precision and reliability.

To create a secure mechanical and optimized electrical interconnection between the cable and the connector, it is desirable to have generally uniform, circumferential contact between a leading edge of the coaxial cable outer conductor and the connector body. A flared end of the outer conductor may be clamped against an annular wedge surface of the connector body via a coupling body. Representative of this technology is commonly owned U.S. Pat. No. 6,793,529 issued Sep. 21, 2004 to Buenz. Although this type of connector is typically removable/re-useable, manufacturing and installation is complicated by the multiple separate internal elements required, interconnecting threads and related environmental seals.

Connectors configured for permanent interconnection via solder and/or adhesive interconnection are also well known in the art. Representative of this technology is commonly owned U.S. Pat. No. 5,802,710 issued Sep. 8, 1998 to Bufanda et al. However, solder and/or adhesive interconnections may be difficult to apply with high levels of quality control, resulting in interconnections that may be less than satisfactory, for example when exposed to vibration and/or corrosion over time.

Passive Intermodulation Distortion, also referred to as PIM, is a form of electrical interference/signal transmission degradation that may occur with less than symmetrical interconnections and/or as electro-mechanical interconnections shift or degrade over time, for example due to mechanical stress, vibration, thermal cycling and/or material degradation. PIM is an important interconnection quality characteristic as PIM from a single low quality interconnection may degrade the electrical performance of an entire RF system.

During interconnection procedures, the coaxial connector and/or coaxial connector may be mounted in a fixture which secures the connector and/or cable in a secure pre-determined orientation with respect to one another. Depending upon the type of interconnection, multiple fixtures and/or mounting/remounting may be required to perform separate portions of the interconnection procedure, such as separately forming secure electro-mechanical interconnections with respect to each of the inner and outer conductors of the coaxial cable. However, each mounting/remounting procedure consumes additional time and/or may provide opportunities for the introduction of alignment errors.

Competition in the coaxial cable connector market has focused attention on improving electrical performance and long term reliability of the cable to connector interconnection. Further, reduction of overall costs, including materials, training and installation costs, is a significant factor for commercial success.

Therefore, it is an object of the invention to provide a coaxial connector and method of interconnection that overcomes deficiencies in the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, where like reference numbers in the drawing figures refer to the same feature or element and may not be described in detail for every drawing figure in which they appear and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention.

FIG. 1 is a schematic partial cut-away external isometric view of an exemplary embodiment of a coaxial cable inserted through a coaxial connector and an inner conductor cap shown spaced away from the end of the inner conductor, prior to initating connector-to-cable interconnection.

FIG. 2 is a schematic partial cut-away isometric view of the coaxial connector of FIG. 1 with the outer conductor sonotrode flaring the leading edge of the outer conductor against the flare seat.

FIG. 3 is a close-up view of area A of FIG. 2.

FIG. 4 is a schematic partial cut-away isometric view of the coaxial connector of FIG. 1 with the outer conductor sonotrode advanced to initiate the flaring of the leading edge of the outer conductor against the flare seat.

FIG. 5 is a schematic partial cut-away isometric view of the coaxial connector of FIG. 1 with the outer conductor sonotrode seated upon the leading end flare and the inner conductor sonotrode advanced to initiate ultrasonic welding of the inner conductor cap upon the inner conductor.

FIG. 6 is a schematic partial cut-away isometric view of the coaxial connector of FIG. 1 with the inner conductor and outer conductor sonotrodes retracted.

FIG. 7 is a schematic partial cut-away isometric view of the coaxial connector of FIG. 1 with interconnection completed.

FIG. 8 is a schematic isometric view of a coaxial cable and coaxial connector ready for insertion into a fixture.

FIG. 9 is a schematic isometric view of the fixture of FIG. 8, with the coaxial cable and the coaxial connector seated in the fixture.

FIG. 10 is a schematic isometric view of the fixture of FIG. 8, closed around the coaxial cable and the coaxial connector, ready for flaring and/or ultrasonic welding via the coaxial inner and outer conductor sonotrodes.

DETAILED DESCRIPTION

Aluminum has been applied as a cost-effective alternative to copper for the conductors in coaxial cables. However, aluminum oxide surface coatings quickly form upon air-exposed aluminum surfaces. These aluminum oxide surface coatings may degrade traditional mechanical, solder and/or conductive adhesive interconnections.

The inventor has recognized that increasing acceptance of coaxial cable with solid outer and/or inner conductors of aluminum and/or aluminum alloy enables connectors configured for interconnection via ultrasonic welding between the outer and inner conductors and a respective connector body and/or inner conductor cap inner contact which may each also be cost effectively provided, for example, formed from aluminum and/or aluminum alloy.

Further with respect to the inner conductor interconnection, the inventor has identified several difficulties arising from the interconnection of aluminum inner conductor coaxial cable configurations with prior coaxial cable connectors having inner contact configurations. Prior coaxial connector mechanical interconnection inner contact configurations are generally incompatible with aluminum inner conductors due to the creep characteristics of aluminum. Further, galvanic corrosion between the aluminum inner conductor and a dissimilar metal of the inner contact, such as bronze, brass or copper, may contribute to accelerated degradation of the electro-mechanical interconnection.

Utilizing friction welding, such as ultrasonic welding, for both the outer conductor to connector body and inner conductor to inner conductor cap interconnections enables a molecular bond interconnection with inherent resistance to corrosion and/or material creep interconnection degradation. Further, a molecular bond interconnection essentially eliminates the opportunity for PIM generation due to shifting and/or degrading mechanical interconnections.

An ultrasonic weld may be formed by applying ultrasonic vibrations under pressure in a join zone between two parts desired to be welded together, resulting in local heat sufficient to plasticize adjacent surfaces that are then held in contact with one another until the interflowed surfaces cool, completing the weld. An ultrasonic weld may be applied with high precision via a sonotrode and/or simultaneous sonotrode ends to a point and/or extended surface. Where a point ultrasonic weld is applied, successive overlapping point welds may be applied to generate a continuous ultrasonic weld.

Ultrasonic vibrations may be applied, for example, in a linear direction and/or reciprocating along an arc segment, known as torsional vibration.

Because the localized abrasion of the ultrasonic welding process can break up any aluminum oxide surface coatings in the immediate weld area, no additional treatment may be required with respect to removing or otherwise managing the presence of aluminum oxide on the interconnection surfaces.

Exemplary embodiments of an inner and outer conductor ultrasonic weldable coaxial connector 2 are demonstrated in FIGS. 1-7. As best shown in FIG. 1, a unitary connector body 4 is provided with a bore 6 dimensioned to receive the outer conductor 8 of a coaxial cable 9 therein. As best shown in FIG. 3, a flare seat 10 angled radially outward from the bore 6 toward a connector end 18 of the connector body 4 is open to the connector end of the coaxial connector 2 providing a mating surface to which a leading end flare 14 of the outer conductor 8 may be ultrasonically welded by an outer conductor sonotrode 16 of an ultrasonic welder inserted to contact the leading end flare 14 from the connector end 18.

One skilled in the art will appreciate that connector end 18 and cable end 12 are applied herein as identifiers for respective ends of both the coaxial connector 2 and also of discrete elements of the coaxial connector 2 and sontotrodes described herein, to identify same and their respective interconnecting surfaces according to their alignment along a longitudinal axis of the connector between a connector end 18 and a cable end 12.

Prior to interconnection via ultrasonic welding, the leading end of the coaxial cable 9 may be prepared, as best shown in FIG. 1, by cutting the coaxial cable 9 so that the inner conductor 24 extends from the outer conductor 8. Also, dielectric material 26 between the inner conductor 24 and outer conductor 8 may be stripped back and a length of the outer jacket 28 removed to expose desired lengths of each.

The inner conductor 24 extending from the prepared end of the coaxial cable 9 may be selected to pass through to the connector end 18 as a portion of the selected connection interface 31. If the selected coaxial cable 9 has an inner conductor 24 that has a larger diameter than the inner conductor portion of the selected connector interface 31, the inner conductor 24 may be ground at the connector end 18 to the required diameter.

Although a direct pass through inner conductor 24 advantageously eliminates interconnections, for example with the spring basket interconnection with a traditional coaxial connector inner contact, such may introduce electrical performance degradation such as PIM. Where the inner conductor 24 is also aluminum material some applications may require a non-aluminum material connection point at the inner contact/inner conductor of the connection interface 31. As shown for example in FIG. 1, an inner conductor cap 20, for example formed from a metal such as brass or other desired metal, may be applied to the end of the inner conductor 24, also by friction welding such as ultrasonic welding.

The inner conductor cap 20 may be provided with an inner conductor socket at the cable end 12 and a desired inner conductor interface 22 at the connector end 4. The inner conductor socket may be dimensioned to mate with a prepared end 23 of an inner conductor 24 of a coaxial cable 9. To apply the inner conductor cap 20, the end of the inner conductor 24 is ground to provide a pin corresponding to the selected socket geometry of the inner conductor cap 20. To allow material inter-flow during welding attachment, the socket geometry of the inner conductor cap 20 and/or the end of the inner conductor 24 may be formed to provide a material gap 25.

A rotation key 27 may be provided upon the inner conductor cap 20, the rotation key 27 dimensioned to mate with an inner sonotrode tool 15 for rotating and/or torsionally reciprocating the inner conductor cap 20, for interconnection via ultrasonic friction welding.

The cable end 12 of the coaxial cable 9 is inserted through the bore 6 and an annular flare operation is performed on a leading edge of the outer conductor 8. The resulting leading end flare 14 may be angled to correspond to the angle of the flare seat 10 with respect to a longitudinal axis of the coaxial connector 2. By performing the flare operation against the flare seat 10, the resulting leading end flare 14 can be formed with a direct correspondence to the flare seat angle. The flare operation may be performed utilizing the leading edge of the outer conductor sonotrode 16, provided with a conical cylindrical inner lip with a connector end 18 diameter less than an inner diameter of the outer conductor 8, for initially engaging and flaring the leading edge of the outer conductor 8 against the flare seat 10.

An overbody 30, as shown for example in FIG. 1, may be applied to the connector body 4 as an overmolding of polymeric material. The overbody 30 increases cable to connector torsion and pull resistance.

Depending upon the applied connection interface 31, demonstrated in the exemplary embodiments herein as a standard 7/16 DIN male interface, the overbody 30 may be provided dimensioned with an outer diameter cylindrical support surface 34 and/or support ridges depending upon the diameter of the selected coaxial cable. Tool flats 39 (see FIG. 8) for retaining the coaxial connector 2 during interconnection with other cables and/or devices may be formed in the cylindrical support surface 34 by removing surface sections of the cylindrical support surface 34.

The coupling nut 36 is retained upon the support surface 34 and/or support ridges at the connector end 18 by an overbody flange 32. At the cable end 12, the coupling nut 36 may be retained upon the cylindrical support surface 34 and/or support ridges of the overbody 30 by applying one or more retention spurs 41 (see FIG. 8) proximate the cable end of the cylindrical support surface 34. The retention spurs 41 are angled with increasing diameter from the cable end 12 to the connector end 18, allowing the coupling nut 36 to be passed over them from the cable end 12 to the connector end 18, but then retained upon the cylindrical support surface 34 by a stop face provided at the connector end 18 of the retention spurs 41.

The overbody 30 may also provide connection interface structure at the connector end 18 and further reinforcing support at the cable end 12, enabling reductions in the size of the connector body 4, thereby potentially reducing overall material costs. For example, the overbody 30 is demonstrated extending from the connector end 18 of the connector body 4 to provide portions of the selected connector interface 31, an alignment cylinder 38 of the 7/16 DIN male interface, further reducing metal material requirements of the connector body 4.

The overbody flange 32 may be securely keyed to a connector body flange 40 of the connector body 4 and thereby with the connector body 4 via one or more interlock apertures 42 such as holes, longitudinal knurls, grooves, notches or the like provided in the connector body flange 40 and/or outer diameter of the connector body 4, as shown for example in FIG. 1. Thereby, as the polymeric material of the overbody 30 flows into the one or more interlock apertures 42 during overmolding, upon curing the overbody 30 is permanently coupled to and rotationally interlocked with the connector body 4.

The cable end of the overbody 30 may be dimensioned with an inner diameter friction surface 44 proximate that of the coaxial cable jacket 28, enabling, for example, an interference fit and/or polymeric friction welding between the overbody 30 and the jacket 28, by rotation of the connector body 4 with respect to the outer conductor 8, thereby eliminating the need for environmental seals at the cable end 12 of the connector/cable interconnection.

The overbody 30 may also have an extended cable portion proximate the cable end provided with a plurality of stress relief apertures 46. The stress relief apertures 46 may be formed in a generally elliptical configuration with a major axis of the stress relief apertures 46 arranged normal to the longitudinal axis of the coaxial connector 2. The stress relief apertures 46 enable a flexible characteristic of the cable end of the overbody 30 that increases towards the cable end of the overbody 30. Thereby, the overbody 30 supports the interconnection between the coaxial cable 9 and the coaxial connector 2 without introducing a rigid end edge along which a connected coaxial cable 2 subjected to bending forces may otherwise buckle, which may increase both the overall strength and the flexibility characteristics of the interconnection.

Where the overbody 30 is interconnected with the jacket 28 via friction welding, friction between the friction surface 44 and the outer diameter of the jacket 28 heats the respective surfaces to a point where they begin to soften and intermingle, sealing them against one another. The jacket 28 and/or the inner diameter of the overbody 30 may be provided as a series of spaced apart annular peaks of a contour pattern such as a corrugation, or a stepped surface, to provide enhanced friction, allow voids for excess friction weld material flow and/or add key locking for additional strength. Alternatively, the overbody 30 may be sealed against the outer jacket 28 with an adhesive/sealant or may be overmolded upon the connector body 4 after interconnection with the outer conductor 8, the heat of the injected polymeric material bonding the overbody 30 with and/or sealing against the jacket 28.

In a method for cable and connector interconnection, the prepared end of the coaxial cable 9 is inserted through the coupling nut 36 (the coupling nut 36 is advanced along the coaxial cable 9 out of the way until interconnection is completed) and connector body bore 6 so that the outer conductor 8 extends past the flare seat 10 a desired distance. The connector body 4 and/or cable end of the overbody 30 may be coated with an adhesive prior to insertion, and/or a spin welding operation may be performed to fuse the overbody 30 and/or cable end of the connector body 4 with the jacket 28. The connector body 4 and coaxial cable 9 are then retained in a fixture 37, rigidly securing these elements for the flaring and electrical interconnection friction welding via ultrasonic welding steps. One skilled in the art will appreciate that the fixture may be any manner of releasable retention mechanism into which the coaxial cable and/or coaxial connector 2 may be easily inserted and then released, for example as demonstrated in FIGS. 8-10.

The flaring operation may be performed with a separate flare tool or via advancing the outer conductor sonotrode 16 to contact the leading edge of the head of the outer conductor 8, as shown for example in FIG. 4, resulting in flaring the leading edge of the outer conductor 8 against the flare seat 10 (See FIG. 3). Once flared, the outer conductor sonotrode 16 is advanced (if not already so seated after flaring is completed) upon the leading end flare 14 and ultrasonic welding may be initiated.

Ultrasonic welding may be performed, for example, utilizing linear and/or torsional vibration. In linear vibration ultrasonic-type friction welding of the leading end flare 14 to the flare seat 10, a linear vibration is applied to a cable end side of the leading end flare 14, while the coaxial connector 2 and flare seat 10 therewithin are held static within the fixture 37. The linear vibration generates a friction heat which plasticizes the contact surfaces between the leading end flare 14 and the flare seat 10. Where linear vibration ultrasonic-type friction welding is utilized, a suitable frequency and linear displacement, such as between 20 and 40 KHz and 20-35 microns, selected for example with respect to a material characteristic, diameter and/or sidewall thickness of the outer conductor 8, may be applied.

With the outer conductor interconnection completed, the outer diameter sonotrode head may be advanced into supporting contact against the leading end flare 14 of the outer conductor 8, further improving the immobilization of the coaxial cable 9 and coaxial connector 2.

As shown in FIG. 5, within a bore of the outer conductor sonotrode 16, the inner conductor sonotrode 15 is then advanced to friction weld the inner conductor cap 20 upon the prepared end 23 of the inner conductor 24. Because the outer conductor sonotrode 16 and the inner conductor sonotrode 15 are arranged coaxially, alignment with the desired coaxial elements of the coaxial cable 9 is ensured, without requiring adjustment of the coaxial cable 9 and/or coaxial connector 2 within the fixture 37.

The inner conductor cap 20 may have been pre-inserted upon the prepared end 23 of the inner conductor 24 or alternatively may be provided loaded into the cable end of the inner conductor sonotrode 15. The inner conductor sonotrode 15 may include a key feature 48 configured to receive and engage the rotation key 27 of the inner conductor cap 20. Utilizing the key feature 48 to drive the inner conductor cap 20, torsional vibration ultrasonic-type friction welding may be applied.

In torsional vibration ultrasonic-type friction welding, a torsional vibration is applied to the interconnection via the inner conductor sonotrode 15 coupled to the inner conductor cap 20 by the rotation key 27, while the coaxial connector 2 and coaxial cable 9 with inner conductor 24 there within are held static within the fixture 37. The torsional vibration generates a friction heat which plasticizes the contact surfaces between the prepared end 23 and the inner conductor cap 20. Where torsional vibration ultrasonic-type friction welding is utilized, a suitable frequency and torsional vibration displacement, for example between 20 and 40 KHz and 20-35 microns, may be applied, also selected with respect to material characteristics and/or dimensions of the mating surfaces.

Alternatively, the inner conductor sonotrode 15 may be applied to interconnect the inner conductor cap 20 and prepared end 23 of the inner conductor 24 and the outer conductor sonotrode 16 then advanced coaxially around the inner conductor sonotrode 15 to perform flaring of the outer conductor leading end flare 14 and/or ultrasonic friction weld interconnection.

Where the outer conductor and inner conductor sonotrodes 16, 15 are independent of one another during operation, a vibration profile comprising a vibration type, frequency and/or amplitude selected according to the requirements of each type of interconnection may be applied. If desired, both the inner conductor and outer conductor sonotrodes 15, 16 may be applied, either with the same vibration profile or separate vibration profiles, simultaneously to further reduce the interconnection time requirements.

As shown for example in FIG. 5, when the interconnection is completed, the inner conductor and outer conductor sonotrodes 15, 16 may be withdrawn and the interconnected coaxial cable 9 and coaxial connector 2 released from the fixture 37. With the coupling nut 36 advanced over the overbody 30 to a ready for interconnection position against the overbody flange 32, the interconnection has been completed, as best shown in FIG. 7.

One skilled in the art will appreciate that the coaxial connector 2 and interconnection method disclosed has significant material cost efficiencies and provides a permanently sealed interconnection with reduced size and/or weight requirements. Because of the coaxial sonotrode configuration, the coaxial cable 9 and coaxial connector 2 need to be mounted in the fixture 37 only once, which simplifies the electrical interconnection procedure. Thereby, the single fixturing feature of the flaring and electrical interconnection method may increase the speed of manufacture and/or improve alignment of the resulting interconnection. Finally, because a molecular bond is established at each electro-mechanical interconnection, PIM resulting from such interconnections may be significantly reduced and/or entirely eliminated.

Table of Parts 2 coaxial connector 4 connector body 6 bore 8 outer conductor 9 coaxial cable 10 flare seat 12 cable end 14 leading end flare 15 inner conductor sonotrode 16 outer conductor sonotrode 18 connector end 20 inner conductor cap 22 inner conductor interface 23 prepared end 24 inner conductor 25 material gap 26 dielectric material 27 rotation key 28 jacket 30 overbody 31 connection interface 32 overbody flange 34 support surface 36 coupling nut 37 fixture 38 alignment cylinder 39 tool flat 40 connector body flange 41 retention spur 42 interlock aperture 44 friction surface 46 stress relief aperture 48 key feature

Where in the foregoing description reference has been made to materials, ratios, integers or components having known equivalents then such equivalents are herein incorporated as if individually set forth.

While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus, methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of applicant's general inventive concept. Further, it is to be appreciated that improvements and/or modifications may be made thereto without departing from the scope or spirit of the present invention as defined by the following claims. 

1. A method for interconnecting a coaxial connector with a solid outer conductor coaxial cable, comprising the steps of: providing a monolithic connector body with a bore; a flare seat angled radially outward from the bore toward a connector end of the connector; inserting a leading end of the coaxial cable into the bore, until a leading end of the solid outer conductor extends beyond the flare seat; flaring the leading end of the solid outer conductor to provide a leading end flare of the outer conductor adjacent the flare seat; ultrasonically welding the leading end flare to the flare seat; and ultrasonically welding an inner conductor cap upon an end of an inner conductor of the coaxial cable.
 2. The method of claim 1, wherein the outer conductor and the connector body are each one of aluminum and aluminum alloy material.
 3. The method of claim 1, wherein the flare seat and the leading end flare of the outer conductor have the same angle.
 4. The method of claim 1, wherein the ultrasonic welding of the leading end flare and flare seat is performed by an outer conductor sonotrode; the ultrasonic welding of the inner conductor cap upon the end of the inner conductor is performed by an inner conductor sonotrode; and the outer conductor sonotrode and the inner conductor sonotrode are coaxial with one another.
 5. The method of claim 4, wherein the inner conductor sonotrode and the outer conductor sonotrode are each operated with a different vibration profile.
 6. The method of claim 4, wherein the ultrasonic welding of the inner conductor cap upon the end of the inner conductor and the ultrasonic welding of the leading end flare and flare seat is performed without releasing the coaxial connector from a fixture.
 7. The method of claim 4, wherein the ultrasonic welding of the leading end flare and flare seat is performed and then, while the outer conductor sonotrode is seated against the outer conductor flare, the ultrasonic welding of the inner conductor cap to the end of the inner conductor is performed. 